Pressurised fluid containers are in widespread use for dispensing a wide variety of materials including cosmetic materials, e.g., deodorants, body fresheners etc., and domestic cleaning materials, e.g., detergents, polishes, waxes etc. Conventional pressurised fluid containers are provided with a valve assembly for dispensing the container contents comprising a hollow, elongate valve member which is movable relative to the body of the container between an outer closed position and an inner dispensing position. The valve member is biased, usually by a spring, to the outer closed position to prevent the discharge of material from the container when not in use. To actuate the valve assembly, the valve member is depressed inwardly by the user to the dispensing position allowing material to exit from the container.
The use of aerosol devices to administer medicament, such as drugs or other therapeutically active compounds, by inhalation therapy is commonplace, particularly for the treatment of respiratory disorders, such as asthma, where it is important that the amount of material dispensed is a predetermined, accurate volume each time the valve is actuated. The aerosol container is charged with a self-propelling liquid composition containing the medicament dissolved or dispersed therein and provided with a valve assembly capable of dispensing metered amounts of the composition. Examples of such valve assemblies are disclosed in British Patent Nos. 864694, 1287126, 1336379, 2004526, 2077229 and 2086845, European Patent No. 191614 and U.S. Pat. Nos. 2,746,796 and 3,738,542.
Many known metering valve assemblies for pressurised aerosol containers comprise a metering chamber positioned at the outlet of the container which is filled with a fresh dose of the material to be dispensed immediately after the previous dose has been dispensed. This feature is incorporated into the valve assembly to avoid the need to prime the assembly before use. A hollow elongate valve member is arranged for reciprocal movement through the metering chamber between a closed, non-dispensing position where the metering chamber is filled with the material to be dispensed and a dispensing position, in which the metered dose of material is dispensed through the valve member to the outside environment. The valve member is again biased to the closed, non-dispensing position. This arrangement allows the dosage of material dispensed from the aerosol container to be accurately reproduced with each operation of the valve.
In such prior art valve assemblies described above, the elongate valve member is biased to its closed, non-dispensing position, normally under the influence of a spring. Generally, a force must be applied to the valve member to overcome the spring and move the valve member to its dispensing position. There may be certain disadvantages to this arrangement of valve assembly, particularly when fitted to aerosol containers for use with certain types of inhalation devices for dispensing medicament to patients in inhalation therapy.
U.S. Pat. No. 4,506,803 discloses a valve assembly for dispensing metered amounts of material from a main reservoir. The valve assembly includes a metering chamber having a pair of apertures that respectively connect the metering chamber to the main reservoir and to the exterior. A valve seal is mounted within each of the apertures. An additional seal is mounted within the metering chamber, with all the seals in substantial alignment. A slidable valve member comprising dispensing and bypass passages is positioned within and co-operable with the seals. The bypass passage selectively interconnects the main reservoir with the metering chamber and the dispensing passage interconnects the metering chamber with the exterior. The seals selectively co-operate with the two passages as the stem is slidably moved through the metering chamber and the reservoir.
The valve member is biased to a non-dispensing position, in which the dispensing passage is sealingly engaged by one of the chamber seals, by a spring mounted exteriorly of the container so that the bypass passage is positioned within the unfilled metering chamber. The metering chamber is isolated from both the main reservoir and from the exterior of the assembly. The valve member is then depressed inwardly to a charging position in which the inlet aperture of the dispensing passage is sealingly engaged by the additional seal mounted within the metering chamber. Accordingly, the metering chamber and the exterior of the apparatus are isolated. In this position a portion of the bypass passage is moved into the main reservoir, thereby placing the main reservoir and the metering chamber in communication via the bypass passage. This charges the metering chamber with a desired amount of fluid material to be dispensed. The valve member is then released so that it will slide into a dispensing position in which the main reservoir and metering chamber are again isolated from one another; the bypass passage moving into sealing engagement with the other valve seal and back into the metering chamber. During this movement of the stem, the inlet aperture of the dispensing passage first moves out of engagement with the additional seal and then into the metering chamber, whereby material from the metering chamber enters the dispensing passage inlet port, moves through the dispensing passage, and is dispensed through a spray nozzle of the dispensing passage. As the valve member continues to be biased exteriorly, the nozzle continues to dispense a pre-determined amount of the material held within the metering chamber until the dispensing passage inlet port again moves into engagement with the first seal and the assembly again assumes the non-dispensing position.
European Patent Application No. 0260067 discloses a metering valve for a pressurised aerosol container which is configured such that the metering chamber exists only upon actuation of the valve stem to dispense the dosage. Thus, the metering chamber is created, filled with aerosol formulation and emptied during the brief moment the valve stem is depressed and subsequently released by the user to dispense a dose. The valve is biased to its non-dispensing position.
Valves which are biased to the dispensing position are known and are disclosed, for example in GB 1200129, 1246710, 1310161, 1311512, 1370885 and 2240930.